Commercial processes for coupling epichlorohydrin and a bisphenol rely on the use of soluble catalysts (U.S. Pat. Nos. 2,772,296 and 3,477,990; French specification No. 1,286,345) or alkaline substances (U.S. Pat. Nos. 2,801,227, 2,986,552 etc.; Belgian specification No. 518,057). However, the use of inorganic bases like caustic produces undesirable by-products and the soluble catalysts must be removed from the final resinous product, which represents an economic loss of effort spent in removing and disposing of catalyst used only once.
Anionic exchange resins have been previously reported as non-soluble catalysts for the coupling of epichlorohydrins and polyhydric phenols (U.S. Pat. No. 3,372,142). The use of these highly crosslinked polymers results in higher levels of undersirable by-products than the soluble catalyst counterpart e.g. benzyltrimethylammonium chloride--a soluble catalyst vs. MSA-1--a macroporous strong anion exchange resin with 4-benzyltrimethylammonium chloride groups as the active specie.
We have developed a catalyst which is not only insoluble but also eliminates the formation of the higher levels of impurities observed with the use of the highly crosslinked anionic exchange resins.